Incidence of Thiopurine-Induced Severe Myelosuppression in a Nationwide Cohort of Patients With Inflammatory Bowel Disease.

INTRODUCTION

There is paucity of data on the incidence of severe thiopurine (TP)-induced myelosuppression (TIM) among patients with inflammatory bowel disease (IBD).

METHODS

Using the Veterans Affairs Healthcare System, we identified patients with IBD with normal pretreatment TP S-methyltransferase levels who received TPs for 6 months and developed severe TIM.

RESULTS

Among 73,392 patients with IBD, 14,760 had received TPs, and 2,823 had a normal TP S-methyltransferase level. The incidence rate of severe TIM was 1.25 per 1,000 patient-years.

DISCUSSION: The incidence of severe TIM was very low, calling into question the necessity of frequent long-term complete blood count monitoring among patients with IBD on TPs.